1. Field of the Invention;
The present invention relates to a dry etching method for an Al.sub.x Ga.sub.1-x N(0.ltoreq.x.ltoreq.1) semiconductor.
2. Description of the Related Art;
Conventionally, the Al.sub.x Ga.sub.1-x N(0.ltoreq.x.ltoreq.1) semiconductor has been watched with keen interest as a material for a light emitting diode emitting a blue light and a light emitting device emitting a light with a short wavelength, and in manufacturing such a device, it is required to establish etching techniques such as mesa etching, recess etching and the like likewise the case of other compound semiconductors.
The Al.sub.x Ga.sub.1-x N semiconductor is a substance which is very stable chemically, and is insoluble in an acid such as hydrochloric acid, sulfuric acid, or hydrofluoric acid or a mixture thereof which is used normally as an etching fluid for other III-V group compound semiconductors. For this reason, a wet etching method using such fluids can not be applied to etching for the Al.sub.x Ga.sub.1-x N semiconductor.
The present inventors developed a dry etching method for the Al.sub.x Ga.sub.1-x N(0.ltoreq.x.ltoreq.1) semiconductor with the plasma gas of carbon tetrachloride (CCl.sub.4) or dichlorodifluoromethane (CCl.sub.2 F.sub.2). (See Japanese Laid-Open Patent Publication Nos. 278025/1989 and 278026/1989, and U.S. Pat. No. 4,946,548.)
However, the carbon tetrachloride (CCl.sub.4) and the dichlorodifluoromethane (CCl.sub.2 F.sub.2) are designated as the substances destroying the ozone layer and are to be completely forbidden to be used by A.D. 2000. Also, the problem is reported that since polymers comprising carbon are formed on the etched surface of the semiconductor in the plasma etching with the gas comprising carbon, the etched surface is lowered in quality.
Predicting a gas having a desirable reaction characteristic in the plasma etching is impossible because the reaction mechanism is affected by the combination and the crystalline structure of atoms of a compound semiconductor to be etched. Accordingly, prediction cannot be made on whether or not an existing reaction gas is effective for etching the Al.sub.x Ga.sub.1-x N semiconductor.
A gas effective for etching the Al.sub.x Ga.sub.1-x N semiconductor is not reported except for the disclosure by the present inventors.